extern int  strcmp(char *, char *);
extern char *strchr(char *, char);
extern void strcpy(char *, char *);
extern char *strdup(char *);
extern int strlen(char *);
extern int  atoi(char *);
extern void itoa(int, char *);
extern void reverse(char *);
extern void memcpy(char *, char *, int);
extern void memset(char*, char, int);

